Background
3-methoxy Tyramine is a natural metabolite of dopamine, produced by catechol O-methyltransferase (COMT). It is a weak agonist of trace amine-associated receptor 1 (EC50 = 1.7 ?M).1 3-methoxy Tyramine levels are assessed to monitor COMT activity in Parkinson’s disease.2 Elevated 3-methoxy Tyramine levels may also indicate abnormal catecholamine synthesis that occurs in certain neuroendocrine tumors.3
1.Wainscott, D.B., Little, S.P., Yin, T., et al.Pharmacologic characterization of the cloned human trace amine-associated receptor1 (TAAR1) and evidence for species differences with the rat TAAR1J. Pharmacol. Exp. Ther.320(1)475-485(2007)
2.Espinoza, S., Managó, F., Leo, D., et al.Role of catechol-O-methyltransferase (COMT)-dependent processes in Parkinson's disease and L-DOPA treatmentCNS Neurol. Disord. Drug Targets11(3)251-263(2012)
3.van Berkel, A., Lenders, J.W., and Timmers, H.J.Diagnosis of endocrine disease: Biochemical diagnosis of phaeochromocytoma and paragangliomaEur. J. Endocrinol.170(3)R910-R119(2014)
Protocol
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Cell experiment:
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The rats are killed by cervical dislocation and the brains are removed and placed on an ice-cooled glass plate. The corpora striata are dissected out and homogenized immediately or stored at -17°C until analyzed. For the estimation of 3-Methoxytyramine hydrochloride 1 mL of the neutralized perchloric acid solution is placed in a glass test tube. One millilitre of a solution of potassium ferricyanide (20 μg/mL) in concentrated ammonium hydroxide is added. After 2 min 0 to 1 mL of a solution of cysteine (1 mg/mL) is added and mixed. The fluorescence of the resulting solution is measured in a spectrophotofluorometer fitted with an interference filter in the fluorescence light path. A blank determination is made by reversing the order of the addition of the ferricyanide-ammonia solution and the solution of cysteine. Authentic 3-Methoxytyramine hydrochloride is also added to a portion of the neutralized eluate and the fluorescence developed to check for quenching[1].
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Animal experiment:
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To assess effects of 3-Methoxytyramine hydrochloride (3-MT) in normal and TAAR1-KO mice, the animals are placed in the locomotor activity chamber and 30 min later various doses of 3-Methoxytyramine hydrochloride are administered i.c.v.. To perform i.c.v. administration in this paradigm, habituated mice are removed from the experimental chamber, briefly restrained, i.c.v. injection cannula is placed into the previously implanted (one week before) guide cannula and infusion of 3-Methoxytyramine hydrochloride or vehicle is performed for 4 minutes when animal is freely moving in a home cage. After infusion, animals are put back into experimental chamber and behavior is monitored for 90 min after administration[1].
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参考文献:
[1]. Sotnikova TD, et al. The dopamine metabolite 3-methoxytyramine is a neuromodulator. PLoS One. 2010 Oct 18;5(10):e13452.
[2]. Guldberg HC, et al. Some observations on the estimation of 3-methoxytyramine in brain tissue. Br J Pharmacol. 1971 Aug;42(4):505-11.
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